feat(openid4vci): add notification endpoint support to issuer2 and wallet2

[DaevMithran]

Description

Implements the optional OpenID4VCI 1.0 notification functionality in issuer2 and wallet2.

Issuer2 changes:

• Adds /openid4vci/notification endpoint.
• Adds notification_id to successful Credential Responses containing credentials.
• Validates the access token, issuance session and notification ID.
• Supports credential_accepted, credential_failure and credential_deleted events in notification endpoint.
• Returns 204 No Content for valid notifications.
• Returns invalid_notification_request or invalid_notification_id when applicable.
• Ignores unknown parameters and Handles idempotent repeated requests..
• Stores the latest notification event and description in the issuance session.
• Enables the endpoint by default while retaining a configuration flag.

Wallet2 protocol client:

• Adds NotificationRequestBuilder to waltid-openid4vci-wallet.
• Sends authenticated notification requests to the issuer.

Wallet2 full issuance flow:

• Integrates notification delivery into WalletIssuanceHandler.
• Sends credential_accepted after all returned credentials are stored.
• Sends credential_failure when credential parsing or storage fails.
• Skips delivery when the issuer does not advertise an endpoint or return a notification ID.
• Treats missing notification information as a successful no-op..

Wallet2 isolated fetch-credential flow:

• Preserves notification_id in FetchCredentialResult.notificationId.
• With storeInWallet=true, resolves issuer metadata using credentialIssuerBaseUrl.
• With storeInWallet=false, returns the notification ID without notifying because the wallet has not accepted or stored the credential.
• Treats missing notification information as a successful no-op..

Type of Change

• bug fix - change which fixes an issue
• new feature - change which adds functionality

Checklist

• code cleanup and self-review
• unit + e2e test coverage
• documentation updated accordingly

Breaking

• OAuth2Provider implementations must now implement the four notification endpoint methods: createNotificationRequest, writeNotificationError overloads, and writeNotificationResponse.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
10 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud